Drought’s Effect On Next Year’s Soybean Crop

Active root nodules, indicated by their pink color, are formed by nitrogen fixing bacteria on the roots of soybean plants.

Many Midwest farmers choose not to use an inoculant for their soybeans. They feel, due to the high number of nitrogen fixing bacteria already in the soil, that inoculating offers little benefit. However, after the record-setting drought of 2012, they may want to reconsider. Jim Beuerlein and Harold Watters, agronomists with the Ohio State University, explain that rhizobia bacteria, the nitrogen fixers responsible for forming root nodules, prefer moist conditions with a soil temperature range of 40-80°F (4-27°C). When soils get too hot or too dry, as many fields did this summer, the bacteria can die off very quickly. Results become much worse when soils are both too hot and dry. Of those that do survive, many will have reduced their capacity for nitrogen fixation in order to survive the extreme conditions. The end result is a greatly decreased and less effective rhizobia bacteria population available for nodule development the following year.

To avoid losing yield, the hope is that farmers will become aware of this and decide that replenishing the nitrogen fixing bacteria in their soil through the use of a soybean seed inoculant is in their best interest. With a less active rhizobia bacteria population in the field, the returns from inoculation should be much greater than what they may otherwise be. This can protect them against any damage that the drought may have had on all soil bacteria, and will help ensure that their crop forms more than enough root nodules for abundant soybean production.